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Jan. 31, 1956 Filed April 26, 1952 G. C. SPORNEY SEWING MACHINE THREAD TENSIONER 2 Sheets-Sheet 1 eorye C Jan. 31, 1956 s. c. SPORNEY 2,733,025

SEWING MACHINE THREAD TENSIONER Filed April 26, 1952 2 Sheets-Sheet 2 Gear 6 CQvorrzey SEWING MACHINE THREAD TENSIONER George C. Sporney, Chicago, Ill., assignor to Birtman Electric Company, a corporation of Illinois Application April 26, 1952, Serial No. 284,549

Claims. (Cl. 242-150) This invention relates to a sewing machine and particularly to a thread tensioner for maintaining a predetermined tension or resistance to pull on the thread as it is pulled from the spool during the sewing operation.

In practically all sewing machines, particularly of the household type, thread is pulled from a spool mounted on the machine by a reciprocating take-up lever that operates in conjunction with the reciprocating needle. This arm has a dual function in that it draws the stitch tight in the seam and at the same time pull's more thread from the spool. These functions are accomplished on the upward movement of the arm. Downward movement of the arm is in timed relationship to the downward movement of the needle so that additional thread is available for the next stitch.

in order to provide a predetermined tension on this thread it is customary to provide: spring urged friction means for grasping the thread at some point between the spool and the take-up lever. Means are usually provided for regulating the pressure of this friction means. Many of these thread tensioners have been quite" bulky and have been so located on the outside of. the machine that the thread often caught on the spring or other portion with resulting fraying and sometimes breaking of the thread. In order to overcome these and other difiiculties and to provide a compact, relatively simple, yet highly efficient thread tensioner, I have invented a de vice wherein the predetermined force on the thread is maintained substantially constant for any given setting of the tensioner and wherein the construction is greatly simplified by employing multi-purpose parts. Furthermore, the thread tensioner. of this invention occupies very little space and the major portion of the bulk of the device is on the interior of the sewing machine head so that it is not only hidden from view but isalso out of the way of the thread and does not interfere with the proper operation of the machine.

The invention will be described as related to the embodiment shown in the accompanying drawings. Of the drawings:

Figure 1 is an end elevation of a sewing machine taken from the head end thereof;

Figure 2 is a fragmentary side elevation of the machine showing the head end thereof;

Figure 3 is a section taken substantially along line 3-3 of Figure 2; and

Figure 4 is a fragmentary section taken substantially along line 4- 4 of Figure 3.

The sewing machine shown in the accompanying drawings comprises the usual base plate supported on a platform 11 and including a vertical standard 12, an overhanging arm 13 and a. head 14. Mounted for reciprocation in the head 14 is a needle bar 15 carrying a needle 16 and a reciprocable hold-down foot bar 17 arranged substantially parallel to the needle bar 15. The bottom of the bar 17 has removably attached thereto a holddown foot 18 in the customary manner. This nited States Patent 0 bar 17 also has attached thereto a thread cutting device 19.

Mounted on a pin 20 on the rear portion of the arm 13 is a thread spool 21 from which the thread 22 is fed. This thread passes from the spool 21 over a wire hook 23 at the upper rear corner of the sewing machine head 14. From this hook the thread passes downwardly and through the thread tensioner 24 and then upwardly through the free end of a take-up spring 25 and through the opening 26a of the reciprocable take-up arm 26. From this arm 26 the thread passes downwardly through the opening in a second wire guide 27 and through a needle bar thread guide 28 to the needle 16 where it is,

threaded through the eye 16a thereof. In the con.- struction shown in the drawings, the guides 23 and 27, thread tensioner 24, and take-up spring 25 are all mounted on a removable end plate 29 held in place to form the end portion of the head 14 by a pair of screws 30. The arm 26 extends through the elongated opening 290. in this end plate. The take-up spring 25 extends through an arcuate opening 29b in this plate that is located adjacent to the periphery of the thread tensioner 24. The

hold-down foot bar l7 and thus the foot 18 are raised and lowered by an operating lever 31 extending from the rear of the head 14.

The sewing machine shown and described operates in the following manner:

During reciprocation of the needle bar 15 and needle 16 the arm 26 moves downwardly as the needle is moved downwardly in forming the stitch. Then as the needle is withdrawn upwardly, the arm 26 moves upwardly at a rapid pace to draw the stitch tight and pull additional thread through the tensioner 24 from the spool 21. Then, when the arm 26 is again lowered with downward movement of the needle 16, this additional thread is available for forming the next stitch. These movements and operations are conventional in many types of household sewing machines. The arcuately movable tension spring 25 serves to maintain the thread 22 taut and to at least partially absorb shock in the thread when the arm 26 starts its upward movement from its lowermost position to tighten the thread in the stitch and withdraw additional thread from the spool. The tensioner 24 applies a predetermined constant friction force on the thread so that the reach of thread between the tensioner and the needle will have a tension thereon.

The improved thread tensioner 24' of this invention includes a tubular bearing 32 extending through the end plate 29. This bearing 32 is provided with an annular inner flange 32a at the inner end of an expanding portion 32b which abuts against the inner surface of the plate 29. A restricted portion 32c in the inner end of this portion 32b extends through this plate 29 and has its outer end threaded. This threaded outer end has attached thereto a tubular nut 33 whose inner end presses against an annular disk 34. This annular disk bears against the outer surface of the plate 29 adjacent the restricted portion 32c and with the expanded portion 32b holds the bearing 32 in locked position. In order to prevent rotation of the disk 34, this disk may be provided with an inwardly extending part 34a extending into an opening in the plate 29 as shown in Fig ure 4.

Extending through the bearing 32 and rotatable therein is a threaded bolt 35 provided with a polygonal, such as a hexagonal head 35a. This head is positioned within a polygonal recess 36a in a manually operable knob 36. The inner end 3512 of the bolt 35 has threads thereon at a relatively steep pitch that are engaged by a nut 37 having diametrically opposite extending Wings 37a and 37!).

Located between the annular inner tapered portion 36b of the knob 36 and the annular disk 34 are a pair of dish shaped disks 38 and 39 placed back to back with the bases in contact with each other. The thread 22 is adapted to be held between these bases so that a frictional tension force will be applied to the thread.

In order to hold the disks 3S and 39 in contact with a predetermined force and thus apply a predetermined force to the thread therebetween, there is provided a leaf spring 40 within the head 14 of the sewing machine having base 40a attached to two raised parts 41 on the inner surface of the end plate 29 and having the opposite end provided with an opening 40!) through which the bolt 35 extends. This end of the spring 40 is provided with two pairs of spaced parallel projecting lugs 4th: and 40d holding the nut wings 37a and 3711 respectively therebetween to prevent rotation of the nut 37. Portions of the lower end of the spring 40 on laterally opposite sides of the opening 40b are provided with raised portions 40:: bearing against the inner surface of the nut 57.

The take-up spring 25 through which the thread 22 extends is provided with a helical inner portion 25:: extending around the expanded portion 32b of the hearing 32. The innermost end 250 of this spring is located within one of a plurality of slots 32d in the inner flange 32a of the bearing 32. By positioning this end 250 in a desired slot 32d the tension on the coiled part 250 of the spring 25 can be predetermined. This predetermined tension, therefore, regulates the amount of force exerted on the reach of thread 22 extending between the thread tensioner 24 and the take-up arm 26.

The knob 36 is adapted to be rotated through slightly less than 360 in regulating the force applied by spring 40 through nut 37, bolt 35' and knob 36 on the outermost disk 39 to hold the disks 38 and 39 in contact. Turning the knob 36 in a clockwise direction, as shown in Figure l, progressively increases this force under increased distortion of the spring 40. Similarly, rotation in a counterclockwise direction decreases this force. The knob 36 is provided with regularly spaced numbers 1 to 11 as shown in Figure 2 in order to indicate the distance that the knob has been turned and thus to indicate the relative force applied to the thread. The outer surface of this knob 36 is provided with an extending projection 36c that engages a stop member 42 extending outwardly from the annular disk 34. This stop member 42 is closely adjacent the knob 36 and disks 38 and 39 but is spaced therefrom to permit positioning the thread around the tensioner 24. As is shown in Figure 2 this stop member may be provided with indicia indicating the direction of rotation of the knob 36 in order to loosen or to tighten the frictional pressure on the thread.

As can be seen from the above structure the rotatable shaft or bolt 35 serves to hold the friction means comprising the disks 3% and 39 in place, apply thread pressure through these disks and permit varying this pressure or rotation of the bolt 35. The bearing 32 also has a plurality of functions. It rotatably supports the bolt 35, supports the pressure disks 38 and 39, serves as a mounting for the spring 25, is provided with a means including the slots 32d for predetermining the force on this spring and serves to lock the entire assembly in place on the end plate 29. Thus the thread tensioner of this invention successfully solves the problems of providing positive control of the thread as it is drawn from the spool and fed to the needle for making successive stitches, permits toe application of a controllable predetermined pressure on the thread to regulate the resistance to pull of the thread from the spool, provides a structure wherein the shock in the thread as it is pulled from the spool is at least partially absorbed and similarly provides a structure that is compact and that employs a minimum number of parts because of the plurality of functions of many of these parts.

In order to reduce the friction between the spring 40 and the nut 37 when the tension setting is changed, the

nut 37 is preferably made of a low friction material such as nylon. This frictional drag is further reduced by making the points of contact between the nut and spring as small as possible such as occurs by providing the raised contacting portions 40:2. Furthermore, these raised and arcuately shaped portions 40c permit movement of the nut 37 along the bolt 32 Without interference caused by other portions of the spring contacting this nut.

The foregoing detailed description is given for clearness of understanding only, and no unnecessary limitations should be understood therefrom as modifications will be obvious to those skilled in the art.

I claim:

1. A thread tensioner comprising, a support member, a threaded bolt extending through said support member, means on the front head end of the bolt for frictionally engaging a thread, a nut on the rear threaded end of the bolt having a low-friction inner surface, means for preventing rotation of the nut on rotation of the bolt, and spring means urging the nut away from the support memher, the spring means having an arcuate projecting portion transverse to the axis of the bolt engaging the inner surface of the nut over a relatively small area to minimize further the frictional drag upon adjusting the spring pressure.

2. A thread tensioner, comprising, a support member, a tubular bearing through said support member having an enlarged end to anchor this one end of the bearing against the rear surface of the support member, the bearing member having its opposite end extending beyond the front surface of said support member, a removable lock piece on said opposite end of the bearing positioned against said front surface of said support member to anchor said opposite end of the bearing thereagainst, and thread pressure applying means operatively carried by said opposite end and bearing against said lock piece, the removable lock piece thereby serving to lock the bearing in place and support the portions of said pressure applying means that are operatively carried by said opposite end.

3. The thread tensioner of claim 2 wherein said lock piece includes a tubular member on said opposite end of said bearing and the tension applying means includes a pair of tension disks removably mounted on said tubular member.

4. The thread tensioner of claim 2 wherein said lock piece includes a tubular member threaded on said opposite end of said bearing, and the tension applying means includes a pair of tension disks removably mounted on the tubular member and a slidable and rotatable member ex: tending through the bearing and operatively pressing against said disks to apply pressure thereto, hold the disks in place and provide for manual adjustment of said pressure.

5. A thread tensioner, comprising, a support member, a bearing mounted thereon, a rotatable bolt extending through the bearing, a nut on the rear end of the bolt, spring means engaging the nut urging the nut and thus the bolt in a rearward direction, and apparatus on the spring holding the nut against rotation, the spring being displaceable to disengage said holding apparatus of the spring from the nut and thus release said nut.

References Cited in the file of this patent UNITED STATES PATENTS 1,518,494 Elcock Dec. 9, 1924 2,058,811 McKean Oct. 27, 1936 2,131,005 Chason Sept. 20, 1938 2,166,770 Casas Robert July 18, 1939 2,518,703 Marsac Aug. 15, 1950 2,609,772 Casas Robert Sept. 9, 1952 FOREIGN PATENTS 414,717 Italy Feb. 4, 1946 

